Abstract

We propose a theoretical model for a laser cooled continuous-wave fiber amplifier. The amplification process takes place in the Yb3+-doped core of a fluoride ZBLAN (ZrF4–BaF2–LaF3–AlF3–NaF) glass fiber, while the cooling process takes place in the cladding, which is doped with thulium. It is shown that for each value of the pump power and amplified signal there is an optimum distribution of the concentration of the Tm3+ along the length of the fiber amplifier, which provides optimum athermal operation. The influence of a small deviation in the input signal power on the temperature of the fiber with a fixed distribution of the Tm3+ ions in the fiber cladding is investigated.